Chapter 4 Review, pages 184–189
Knowledge
1. (a)
2. (b)
3. (d)
4. (a)
5. (d)
6. (c)
7. (b)
8. (d)
9. (b)
10. (d)
11. False. If a substance changes colour, a chemical change might have occurred.
12. False. A catalyst speeds the rate of a chemical reaction without being used up.
13. False. Two simple reactants combine to form a more complex product in a synthesis reaction.
14. False. Calcium carbonate (CaCO3) forms calcium oxide and carbon dioxide gas when heated.
15. True
16. False. We can use the activity series to determine whether a displacement reaction will occur.
17. False. A single displacement reaction takes the form A + BC → AC + B.
18. False. Mercury is the only metal that is liquid at room temperature.
19. True
20. (a) (iv)
(b) (i)
(c) (ii)
(d) (iii)
21. Four clues that may indicate that a chemical reaction has taken place are an unexpected
change in colour, the release or absorption of energy, the production of a gas, and the formation
of a precipitate.
22. A catalyst is a substance that makes a reaction occur faster without being used up in the
reaction.
23. In a balanced chemical equation, the total number of atoms of each type in the reactants is the
same as in the products.
24. In a chemical equation, coefficients are multipliers that appear before a chemical formula.
They indicate how many units of each substance are present. Coefficients can be changed to
balance a chemical equation. Subscripts are numbers written below and to the right of a chemical
symbol. They indicate how many atoms or ions of that element are present in one molecule or
formula unit of that substance. Subscripts describe the composition of a substance and cannot be
changed without describing a different substance.
25. This change is a synthesis reaction because two simpler reactants, carbon dioxide and water,
combined to form a more complex product, carbonic acid.
26. The general pattern for a decomposition reaction is: AB → A + B.
27. Decomposition reactions generally require energy, such as electricity or heat, to proceed.
28. During a synthesis reaction of water, hydrogen and oxygen gases are combined to form
water. During a decomposition reaction of water, water is broken down into hydrogen gas and
oxygen gas. The reactants of one reaction are the products of the other. Therefore, the synthesis
and decomposition of water are opposite reactions.
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29. Unlike burning garbage, gasification involves heating waste to a temperature so high that the
molecules of the garbage decompose into simpler substances.
30. Plasma gasification results in a mixture of mostly hydrogen and carbon monoxide called
syngas. Syngas can be burned to generate electricity that could not only power the gasification
plant, but also produce excess that can be sold or used to make industrial chemicals.
31. Three concerns about the gasification of landfill garbage are that gasification may release
harmful emissions into the air, it may undermine recycling efforts, and it may pose risks that are
not yet identified because it is a new technology in Ontario.
32. The activity series of metals is a ranking of metals according to their reactivity. The most
reactive metals are at the top of the list and the least reactive metals are at the bottom.
33. A metal in the activity series will displace any other metal below it from a solution of a
compound. Generally, the least reactive metal is left as an element. Displacement is unlikely to
occur between two metals that are close together on the list. The farther apart the two metal are,
the more likely a displacement reaction will occur.
34. Fluorine is at the top of the halogen activity series. That indicates that fluorine displaces all
other halogens from compounds.
35. Mercury is different from other metals because it is one of the few metals that are found in
nature as pure elements, and it is the only metal that is liquid at room temperature.
36. The general pattern of a single displacement reaction is A + BC → AC + B. That is, one
element A displaces another element B from a compound BC. The general pattern of a double
displacement reaction is AB + CD → AD + BC. That is, two elements A and C displace each
other from their compounds.
37. The precipitate that results from a precipitation reaction is in solid state.
38. The symbol (aq) means aqueous or in water. In a chemical equation, it indicates that the
substance is dissolved in water.
Understanding
39. (a) Step 1. Count the number of atoms of each type on either side of the arrow.
NaClO3 → NaCl + O2
1 Na
1 Na
1 Cl
1 Cl
3O
2O
Step 2. NaClO3 on the left must be multiplied by 2 and O2 on the right must be multiplied by 3 to
balance the oxygen atoms.
2 NaClO3 → 2 NaCl + 3 O2
2 Na
2 Na
2 Cl
2 Cl
6O
6O
Step 3. Write the final chemical equation.
The balanced chemical equation is:
2 NaClO3(s) → 2 NaCl(s) + 3 O2(g)
(b) Step 1. Count the number of atoms of each type on either side of the arrow.
C2H2 + O2 → H2O + CO2
2C
1C
2H
2H
2O
3O
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Step 2. H2O on the right must be multiplied by 2 to balance the oxygen atoms, and CO2 must
then be multiplied by 4 to balance the carbon atoms.
2 C2H2 + 5 O2 → 2 H2O + 4 CO2
4C
4C
4H
4H
10 O
10 O
Step 3. Write the final chemical equation.
The balanced chemical equation is:
2 C2H2(g) + 5 O2(g) → 2 H2O(g) + 4 CO2(g)
(c) Step 1. Count the number of atoms of each type on either side of the arrow.
Na + H2O → NaOH + H2
1 Na
1 Na
2H
3H
1O
1O
Step 2. H2O on the left must be multiplied by 2 to balance the hydrogen atoms, and thus the
oxygen atoms.
2 Na + 2 H2O → 2 NaOH + H2
2 Na
2 Na
4H
4H
2O
2O
Step 3. Write the final chemical equation.
The balanced chemical equation is:
2 Na(s) + 2 H2O(l) → 2 NaOH(aq) + H2(g)
40. (a) Step 1. Count the number of atoms and ions of each type on either side of the arrow.
Ca + HNO3 → H2 + Ca(NO3)2
1 Ca
1 Ca2+
1 H+
2H
−
1 NO3
2 NO3−
Step 2. HNO3 on the left must be multiplied by 2 to balance the NO3− ions.
Ca + 2 HNO3 → H2 + Ca(NO3)2
1 Ca
1 Ca2+
2 H+
2H
−
2 NO3
2 NO3−
Step 3. Write the final chemical equation.
The balanced chemical equation is:
Ca + 2 HNO3 → H2 + Ca(NO3)2
(b) Step 1. Count the number of ions of each type on either side of the arrow.
Fe(NO3)3 + (NH4)2CO3 → Fe2(CO3)3 + NH4NO3
1 Fe3+
2 Fe3+
3 NO3−
1 NO3−
2 NH4+
1 NH4+
1 CO32−
3 CO32−
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Step 2. Fe(NO3)3 on the left must be multiplied by 2 to balance the Fe3+ ions, and (NH4)2CO3
must be multiplied by 3 to balance the CO32− ions.
2 Fe(NO3)3 + 3 (NH4)2CO3 → Fe2(CO3)3 + 6 NH4NO3
2 Fe3+
2 Fe3+
6 NO3−
6 NO3−
+
6 NH4
6 NH4+
3 CO32−
3 CO32−
Step 3. Write the final chemical equation.
The balanced chemical equation is:
2 Fe(NO3)3 + 3 (NH4)2CO3 → Fe2(CO3)3 + 6 NH4NO3
(c) Step 1. Count the number of ions of each type on either side of the arrow.
AgNO3 + K2Cr2O4 → Ag2Cr2O4 + KNO3
1 Ag+
2 Ag+
1 NO3−
1 NO3−
+
2K
1 K+
1 Cr2O42−
1 Cr2O42−
Step 2. AgNO3 on the left must be multiplied by 2 to balance the Ag+ ions, and KNO3 on the
right must be multiplied by 2 to balance the K+ ions.
2 AgNO3 + K2Cr2O4 → Ag2Cr2O4 + 2 KNO3
2 Ag+
2 Ag+
2 NO3−
2 NO3−
+
2K
2 K+
1 Cr2O42−
1 Cr2O42−
Step 3. Write the final chemical equation.
The balanced chemical equation is:
2 AgNO3 + K2Cr2O4 → Ag2Cr2O4 + 2 KNO3
41. Step 1. Count the number of atoms of each type on either side of the arrow.
C6H12O6 + O2 → CO2 + H2O
6C
1C
12 H
2H
8O
3O
Step 2. CO2 and H2O on the right must be multiplied by 6 to balance the carbon and hydrogen
atoms. Then multiply O2 on the left by 6 to balance the oxygen atoms.
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O
6C
6C
12 H
12 H
18 O
18 O
Step 3. Write the final chemical equation.
The balanced respiration equation is:
C6H12O6(aq) + 6 O2(aq) → 6 CO2(aq) + 6 H2O(l) + energy
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42. (a) Any three of the following are clues that a chemical reaction has occurred: an unexpected
change in colour, the release or absorption of energy, the production of a gas, and the formation
of a precipitate.
(b) None of the clues in (a) are conclusive proofs that a chemical reaction has taken place. For
example, heating water until it boils produces a gas, but there is no new substance formed;
shining light on a substance allows it to change colour, but no new substance is formed; rubbing
a substance releases energy, but no new substance is formed; drying a salt solution forms a
precipitate of salt, but no new substance is formed.
43. (a) The reaction is a decomposition reaction.
(b) The reaction is a synthesis reaction.
(c) The reaction is a synthesis reaction.
(d) The reaction is a decomposition reaction.
44. (a) The reactant fits the pattern of a decomposition reaction.
AB → A + B
The products of the reaction would be mercury and oxygen.
The balanced chemical equation is:
2 HgO → 2 Hg + O2
(b) The reactants fit the pattern of a synthesis reaction.
A + B → AB
The product of the reaction would be sodium oxide.
The balanced chemical equation is:
4 Na + O2 → 2 Na2O
(c) The reactant fits the pattern of a decomposition reaction.
AB → A + B
The products of the reaction would be nitrogen and hydrogen.
The balanced chemical equation is:
2 NH3 → N2 + 3 H2
45. (a) The gas is carbon dioxide.
(b) The balanced chemical equation for the decomposition reaction is:
Ag2CO3 → Ag2O + CO2
46. The balanced chemical equation for the decomposition reaction is:
2 H2O → 2 H2 + O2
47. (a) The type of chemical reaction involved in the process of gasification is decomposition.
(b) The conditions required for plasma gasification are a sealed chamber with almost no oxygen
and extremely high temperatures.
(c) The product of plasma gasification, syngas, must be chemically treated by a process called
“scrubbing” to remove contaminants before further use.
48. (a) Zinc will react with a solution of lead(II) sulfate.
(b) The metal zinc is higher than the metal in the compound, lead, on the activity series.
Therefore, a displacement reaction will occur.
(c) A metal higher than Pb on the activity series, such as aluminum, would react with lead(II)
sulfate.
(d) A metal lower than Pb on the activity series (including H), such as silver, would not react
with lead(II) sulfate.
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49. (a) Nickel would not react with sodium chloride.
(b) The metal nickel is lower than sodium on the activity series, so it would not displace sodium
from the compound and no reaction would occur.
50. (a) Step 1. Write the chemical formulas of the reactants and the atoms and ions involved in
the reaction.
Al(s)
H2SO4(aq)
Al
H+ SO42−
A
+ BC → AC + B
Step 2. Identify which is higher on the activity series, the metal element or hydrogen.
Al is higher than H. Therefore, a displacement reaction will occur.
Step 3. Determine the chemical formula of the new compound AC. The remaining element is
displaced.
Al3+
SO42−
Al2(SO4)3
Step 4. Write the balanced chemical equation for the reaction.
The balanced chemical equation is:
2 Al(s) + 3 H2SO4(aq) → Al2(SO4)3(aq) + 3 H2(g)
(b) Step 1. Write the chemical formulas of the reactants and the atoms and ions involved in the
reaction.
Zn(s)
Cu(NO3)2(aq)
Zn
Cu2+ NO3−
A
+ BC → AC + B
Step 2. Identify which is higher on the activity series, the metal element or copper.
Zn is higher than Cu. Therefore, a displacement reaction will occur.
Step 3. Determine the chemical formula of the new compound AC. The remaining element is
displaced.
Zn2+
NO3−
Zn(NO3)2
Step 4. Write the balanced chemical equation for the reaction.
The balanced chemical equation is:
Zn(s) + Cu(NO3)2(aq) → Zn(NO3)2(aq) + Cu(s)
(c) Step 1. Write the chemical formulas of the reactants and the atoms and ions involved in the
reaction.
Au(s)
KNO3(aq)
Au
K+ NO3−
A
+ BC → AC + B
Step 2. Identify which is higher on the activity series, the metal element or potassium.
K is higher than Au. Therefore, no reaction occurs.
51. (a) A single displacement reaction occurs.
(b) The balanced chemical equation for the reaction is: Cl2(g) + 2 KI(aq) → 2 KCl(aq) + I2(aq)
52. (a) A single displacement reaction occurs.
(b) Hydrogen gas is produced.
(c) The balanced chemical equation for the reaction is:
2 Fe(s) + 3 H2SO4(aq) → Fe2(SO4)3(aq) + 3 H2(g)
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53. (a) The source of atmospheric bromine is seawater, which contains dissolved bromide ions.
(b) Scientists believe that, in the presence of sunlight, stable bromide ions lose one electron to
form highly reactive bromine atoms.
(c) Bromine and bromine monoxide may react with elemental mercury in the air to produce
mercury(II) ions. The ions may become attached to snowflakes and fall to the ice surface, thus
being trapped in the ice and snow.
54. (a) Potassium bromide is very soluble in water.
(b) Sodium carbonate is very soluble in water.
(c) Silver acetate is slightly soluble in water.
55. (a) The chemical equation that includes all state symbols is:
CdSO4(aq) + H2S(aq) → CdS(s) + H2SO4(aq)
(b) A precipitate of cadmium sulfide, CdS, would be formed in the reaction.
(c) The differences in solubility of compounds help determine whether any precipitates form
during a double displacement reaction.
Step 1. Write the chemical formulas of the reactants.
CdSO4(aq)
H2S(aq)
Step 2. Separate the reactants into their ions.
Cd2+ SO42−
H+ H+ S−
Step 3. Combine cations and anions to form new compounds.
CdS
H2SO4
Step 4. Check for low solubility.
CdS is slightly soluble, while H2SO4 is very soluble. Therefore, CdS should precipitate.
56. (a) The chemical formula of the precipitate is Ni(OH)2.
(b) The precipitate is a product of a double displacement reaction between sodium hydroxide and
nickel(II) chloride.
Step 1. Write the chemical formulas of the reactants.
NaOH(aq)
NiCl2(aq)
Step 2. Separate the reactants into their ions.
Na+ OH−
Ni2+ Cl− Cl−
Step 3. Combine cations and anions to form new compounds.
NaCl
Ni(OH)2
Step 4. Check for low solubility.
Ni(OH)2 is slightly soluble, while NaCl is very soluble. Therefore, the precipitate is Ni(OH)2.
57. (a) The balanced chemical equation for the reaction is:
CaCO3(s) + 2 HCl(aq) → CO2(g) + H2O(l) + CaCl2(aq)
(b) The bubbles are due to the release of carbon dioxide gas.
(c) This is a useful test for limestone because the test can easily be carried out to identify whether
a mineral is limestone without heating or without any complicated experimental setup.
58. (a) The balanced chemical equation for the reaction is:
NH4NO3(s) → N2O(g) + 2 H2O(g)
(b) The reaction is decomposition reaction.
(c) The balanced chemical equation for the alternative process is:
2 NH3(g) + 2 O2(g) → N2O(g) + 3 H2O(l)
(d) The reaction described in part (c) is a double displacement reaction since nitrogen and part of
the oxygen in O2 displace each other to form two new compounds.
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59. (a) The balanced chemical equation for the process is:
O2(g) + H2(g) → H2O2(l)
(b) The reaction is synthesis reaction.
(c) The purpose of a catalyst is to speed up a reaction without itself being consumed in the
reaction.
(d) If a hydrogen peroxide processing plant does not have the correct catalyst, the synthesis of
hydrogen peroxide would take much longer or the reaction may never achieve the desired yield.
60. (a) A synthesis reaction is likely to take place between calcium metal and oxygen gas.
(b) A neutralization reaction is likely to take place between hydrocyanic acid and sodium
hydroxide solution.
61. (a) The equation represents a double displacement reaction since it fits the general pattern
AB + CD → AD + BC. That is, two elements A and C displace each other from their
compounds. In the equation HF(aq) + KOH(aq) → KF(aq) + H2O(l), H and K displace each
other from the compounds HF and KOH.
(b) The equation represents a single displacement reaction since it fits the general pattern A +
BC → AC + B. That is, one element A displaces another element B from a compound BC. In the
equation Al(s) + Cr2O3(s) → Al2O3(s) + Cr(s), Al displaces Cr from Cr2O3.
62. (a) Step 1. Count the number of ions of each type on either side of the arrow.
AlCl3 + AgNO3 → AgCl + Al(NO3)3
1 Al3+
1 Al3+
3 Cl−
1 Cl−
1 Ag+
1 Ag+
1 NO3−
3 NO3−
Step 2. AgNO3 on the left must be multiplied by 3 to balance the NO3− ions, and AgCl on the
right must be multiplied by 3 to balance the Cl− ions.
AlCl3 + 3 AgNO3 → 3 AgCl + Al(NO3)3
1 Al3+
1 Al3+
−
3 Cl
3 Cl−
3 Ag+
3 Ag+
3 NO3−
3 NO3−
Step 3. Write the final chemical equation.
The balanced chemical equation is: AlCl3(aq) + 3 AgNO3(aq) → 3 AgCl(s) + Al(NO3)3(aq)
The reaction is a double displacement reaction since it fits the pattern AB + CD → AD + BC,
where Al and Ag displace each other from their compounds.
(b) Step 1. Count the number of atoms and ions of each type on either side of the arrow.
Li + H2SO4 → Li2SO4 + H2
1 Li
2 Li+
+
2H
2H
2−
1 SO4
1 SO42−
Step 2. Li on the left must be multiplied by 2 to balance the lithium atoms or ions.
2 Li + H2SO4 → Li2SO4 + H2
2 Li
2 Li+
+
2H
2H
1 SO42−
1 SO42−
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Step 3. Write the final chemical equation.
The balanced chemical equation is: 2 Li(s) + H2SO4(aq) → Li2SO4(aq) + H2(g)
The reaction is a single displacement reaction since it fits the pattern A + BC → AC + B, where
Li displaces H from the compound H2SO4.
(c) Step 1. Count the number of ions of each type on either side of the arrow.
H2SO4 + NaOH → H2O + Na2SO4
2 H+
1 H+
2−
1 SO4
1 SO42−
1 Na+
2 Na+
1 OH−
1 OH−
Step 2. NaOH on the left must be multiplied by 2 to balance the Na+ ions, and H2O on the right
must be multiplied by 2 to balance the H+ ions.
H2SO4 + 2 NaOH → 2 H2O + Na2SO4
2 H+
2 H+
2−
1 SO4
1 SO42−
2 Na+
2 Na+
2 OH−
2 OH−
Step 3. Write the final chemical equation.
The balanced chemical equation is: H2SO4(aq) + 2 NaOH(aq) → 2 H2O(l) + Na2SO4(aq)
The reaction follows the pattern of double displacement reaction but it is classified as a
neutralization reaction since it is a reaction of an acid and a base, and water is one of the
products.
63. (a) Lead(II) nitrate will react with sodium iodide.
(b) Step 1. Write the chemical formulas of the reactants.
Pb(NO3)2(aq)
NaI(aq)
Step 2. Separate the reactants into their ions.
Pb2+ NO3− NO3− Na+ I−
Step 3. Combine cations and anions to form new compounds.
PbI2
NaNO3
Step 4. Check for low solubility.
PbI is slightly soluble, while NaNO3 is very soluble. Therefore, PbI2 should precipitate. That is, a
new substance is formed, an evidence of a chemical reaction.
(c) The balanced chemical equation for the reaction is:
Pb(NO3)2(aq) + 2 NaI(aq) → PbI2(s) + 2 NaNO3(aq)
(d) The precipitate that forms is lead(II) iodide.
Analysis and Application
64. (a) Zn(s) + 2 HCl(aq) → ZnCl2(aq) + H2(g)
(b) Answers may vary. Sample answer: Measure the mass of zinc metal used. Then measure the
total mass of the reactants, including the unknown metal, before the reaction. When the reaction
is complete, measure the total mass of the final solution. The difference in mass should equal the
mass of hydrogen gas that has been given off. If the difference is greater than the expected loss
in mass due to the release of hydrogen, the unknown metal must have also reacted to produce
more hydrogen. The unknown metal is not a catalyst in this reaction since a catalyst should not
be used up during a reaction.
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Chapter 4: The Effects of Chemical Reactions
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65. Answers may vary. Sample answer: Measure the total mass of the reactants before the
reaction. When the reaction is complete, measure the total mass of the products. According to the
law of conservation of mass, the mass of the reactants should equal the mass of the products. If
the mass of the products is less than the mass of the reactants, the loss in mass must be due to a
gaseous product escaping from the reaction mixture.
66. (a) The chemical formulas of the reactants are: Pb(NO3)2 for lead (II) nitrate, and KI for
potassium iodide. The formulas of the products are: PbI2 for lead(II) iodide, and KNO3 for
potassium nitrate.
(b) The balanced chemical equation for the reaction is:
Pb(NO3)2(aq) + 2 KI(aq) → PbI2(s) + 2 KNO3(aq)
(c) Answers may vary. Sample answer: Since there is no gaseous product for the reaction, the
reaction can be used to demonstrate the law of conservation of mass. To demonstrate this law,
measure the total mass of the reactants before the reaction. When the reaction is complete,
measure the total mass of the products. According to the law of law of conservation of mass, the
mass of the reactants should equal the mass of the products.
67. (a) The chemical formula for mercury(II) oxide is HgO.
(b) The products of the reaction are Hg and O2.
(c) The balanced chemical equation for the decomposition reaction is:
2 HgO(s) → 2 Hg(l) + O2(g)
68. (a) The chemical formula for hydrogen is H2 and that for bromine is Br2.
(b) The product of the synthesis reaction is hydrogen bromide, HBr.
(c) The balanced chemical equation for the synthesis reaction is:
Br2(l) + H2(g) → 2 HBr(g)
69. (a) Since potassium is higher than sodium on the activity serious, sodium cannot displace
potassium from a solution of potassium chloride. Therefore, no single displacement reaction
will occur.
(b) Since there is no reaction, the equation for this reaction is:
Na(s) + KCl(aq) → no reaction
70. (a) In this reaction between an element and a compound, the chemist can look at the relative
positions of the element zinc and hydrogen from the compound on the activity series. If the
element is at a higher position, the reaction proceeds.
(b) Zinc is higher than hydrogen on the activity series. Therefore, zinc can react with sulfuric
acid to displace hydrogen from the acid.
71. (a) Zinc is higher than iron on the activity series. Since zinc is more reactive iron, water will
more likely react with the zinc than the iron, thus protecting the iron in the hull of the ship.
(b) Silver is lower than iron on the activity series. Since silver is less reactive the iron, water will
be more likely react with the zinc than the silver. Using silver would not have the desired effect.
(c) Any metal higher than iron on the activity series, such as nickel, would be effective in
slowing corrosion. Any metal lower than iron on the activity series, such as gold, would not be
effective.
72. (a) The balanced chemical equation for the reaction is:
LiCl(aq) + AgNO3(aq) → AgCl(s) + LiNO3(aq)
(b) Answers may vary. Sample answers: To test if all silver ions had been precipitated, filter the
solution to remove the silver chloride precipitate. Since the formation of a precipitate indicates
that there are silver ions present, add an excess amount of lithium chloride solution until no more
precipitate is observed.
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73. (a) The reaction will occur since a new compound can precipitate from the solution.
The balanced chemical equation for the reaction is:
BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2 NaCl(aq)
(b) The reaction will occur since a new compound can precipitate from the solution.
The balanced chemical equation for the reaction is:
Ba(NO3)2(aq) + K2CO3(aq) → BaCO3(s) + 2 KNO3(aq)
(c) The reaction will occur since a new compound can precipitate from the solution.
The balanced chemical equation for the reaction is:
MgCl2(aq) + 2 NaOH(aq) → Mg(OH)2(s) + 2 NaCl(aq)
(d) The reaction will not occur since the cations in the reactants cannot trade places to form a
precipitate, or form a gaseous product, or form a more neutral solution.
74. (a) The balanced chemical equation for the reaction is:
Mg(OH)2(s) + 2 HCl(aq) → 2 H2O(l) + MgCl2(aq)
(b) This is a neutralization reaction since it is a reaction of an acid with a base.
75. (a) The balanced chemical equation for the reaction is:
SiO2(s) + 3 C(s) → SiC(s) + 2 CO(g)
(b) The reaction is a double displacement reaction since silicon and some of the carbon in the
reactants displace each other to form two new compounds.
76. The balanced chemical equation for the reaction is:
HNO3(aq) + KOH(aq) → H2O(l) + KNO3(aq)
77. (a) A base can neutralize hydrofluoric acid. However, to ensure that all acid is neutralized, an
exact amount of the base must be used. Since many of the bases are unsafe to use, instead of a
base, sodium hydrogen carbonate (baking soda) is a compound that can be used to neutralize the
acid as it is safe to store and handle.
(b) The balanced chemical equation for the reaction is:
NaHCO3(s) + HF(aq) → NaF(s) + H2O(g) + CO2(g)
Evaluation
78. (a) Answers may vary. Sample answer: The proposal would work because aluminum is
higher than silver on the activity series and it can displace silver from a solution of silver
compound as a precipitate.
(b) The balanced chemical equation for the single displacement reaction is:
Al(s) + 3 AgNO3(aq) → 3 Ag(s) + Al(NO)3(aq)
79. To precipitate toxic metals from water, the compounds that the metals form with sodium
carbonate or sodium sulfate must be insoluble. Since the carbonates of most metals are insoluble
while of some of their sulfates are soluble, sodium carbonate should be used for this purpose.
80. (a) Answers may vary. Sample answer: This proposal would work because copper is lower
than hydrogen on the activity series. It would not react with sulfuric acid to displace the
hydrogen in the compound.
(b) Answers may vary. Sample answer: Metals lower than hydrogen on the activity series would
not react with sulfuric acid. Therefore, silver and gold are two alternative metals for the outer
skin of the probe. However, a thick plating of silver or gold would be too costly for this purpose
so copper would be a better choice.
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Chapter 4: The Effects of Chemical Reactions
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Reflect on Your Learning
81. Answers may vary. Students’ answers should relate to their understanding of the chemical
reactions in this chapter. Sample answer: I found it surprising that some elements can displace
some other elements out of a compound, but cannot displace a different element. I did not know
that there was an activity series that described this.
82. (a) Answers may vary. Students’ answers would likely relate to the topics in this chapter
about chemical reactions. Sample answer: How much acid do I need to add to a base to
neutralize it?
(b) Answers may vary. Students’ answers should correspond to their questions in part (a).
Sample answer: I could use the Internet to research methods that I could use for determining the
amount of acid that I should add to neutralize a base.
83. Answers may vary. Sample answer: I have learned more about how difficult it can be to
remove toxic metals from water. It requires chemical processes that are probably expensive and
difficult to perform. This makes it more clear how important it is not to pollute in the first place,
since cleanup can be so difficult.
Research
84. Answers may vary. Students’ answers should include a chart that compares the advantages
and disadvantages of using the hydrogen fuel cell technology, and a paragraph of their opinion
on this technology based on their research. Sample answer:
Using Hydrogen Fuel Cell Technology
Advantages
Disadvantages
• Uses a catalyst to make the reaction occur.
• Requires the use of a catalyst that is very
The catalyst is reusable.
expensive. Currently the limiting factor for
• Does not produce fossil fuels when operated. cost-effective hydrogen fuel cells.
• The technology is improving with time to be • Needs a good catalyst for a fast reaction.
more efficient.
• The storage and transport of hydrogen needed
is costly.
85. Answers may vary. Students’ answers should follow the guidelines to answer the different
parts of the question.
Sample answer: Initially, coal and peat powered gasification processes, and the resulting gas was
used as an energy source for cooking and lighting. The gas was developed into an energy source
for blast furnaces and was used as a source of energy during both world wars. Processes used for
gasification include the counter-current fixed bed (“up draft”) gasifier, the co-current fixed bed
(“down draft”) gasifier, the fluidized bed reactor, and the entrained flow gasifier. Worldwide,
gasification has been used for almost 100 years in the production of synthetic chemicals.
Currently, its primary use is in the production of electricity. The gas produced from the
gasification of fossil fuels is burned to produce gases that turn turbines to produce electricity.
Other uses exist, such as fueling modified diesel engines.
Sample answers for decision on additional funds: (for) I think additional funds should be directed
toward gasification processes because the results can be used instead of fossil fuels, which are
non-renewable resources. OR (against) I don’t think additional funds should be directed toward
gasification processes because many of the processes use fossil fuels in the production of the
gases. I think the funds should go to making current use of fossil fuels more efficient.
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Chapter 4: The Effects of Chemical Reactions
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86. Answers may vary. Students’ answers should follow the guidelines to answer the different
parts of the question. Sample answer: Mercury is a liquid at room temperature, but it vaporizes
easily. It is toxic to humans and is easily absorbed through the skin or mucous membranes. A
fetus is most vulnerable to negative effects of mercury in the mother’s bloodstream. A child who
was exposed to mercury before birth might exhibit negative effects on memory, attention,
cognitive thinking, language, and visual spatial and fine motor skills. In adults, problems with
peripheral vision, muscle weakness, and coordination of movement, speech, walking, and
hearing might be observed. Students’ diagrams should show mercury-contaminated food at the
bottom of the food chain and a human at the top. The chain might show a small, mercurycontaminated fish eaten by a larger fish, which is then eaten by a human.
Sample answers for continued research: (for) I think further research into the
disappearance of mercury in the Arctic is necessary because any mercury removed from the air
might possibly find its way into a food chain that might affect human health. OR (against) I think
further research into the disappearance of mercury in the Arctic is not necessary because the
amount is small, and it is mostly isolated from areas where food sources are obtained. The
money should be spent on developing safe food sources close to home.
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Chapter 4: The Effects of Chemical Reactions
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Sample answer for ozone depletion: Although there is currently no ozone hole over the
Arctic, some scientists predict that one will soon appear. Lack of ozone in the atmosphere results
in infrared radiation from space reaching Earth and affecting the organisms. A hole in the ozone
layer would affect many more people than a hole in the Antarctic does because of the distribution
of the population on Earth: more people live in the northern hemisphere than in the southern
hemisphere.
87. Answers may vary. Students’ answers should follow the guidelines to answer the different
parts of the question. Students should explain that acid deposition can form as a result of two
processes. In some cases, hydrochloric acid can be expelled directly into the atmosphere. More
commonly it is due to secondary pollutants that form from the oxidation of nitrogen oxides or
sulfur dioxide gases that are released into the atmosphere. More than 95 % of the elevated levels
of nitrogen oxides in the atmosphere are the result of human activities and the remaining 5 %
comes from several natural processes. Students should then present some solutions to the acid
precipitation problem and include reasonable arguments to support their suggestion.
88. Answers may vary. Students’ answers should follow the guidelines to answer the different
parts of the question. Students should find that the Haber process is used to generate both
fertilizer and explosives. This is the fundamental question about his work. Fertilizer has
undoubtedly helped society, but explosives have been used in wars ever since. Students should
include a discussion on this. As it is a complex issue, it is acceptable to take a position
somewhere in the middle.
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